The federal government’s National Energy Guarantee aims to reduce greenhouse gas emissions in the electricity industry by 26% of 2005 levels. But for Australia to meet its Paris climate change commitments, this 26% reduction will need to be replicated economy-wide.

In sectors such as aviation this is going to be very costly, if not impossible. Our modelling of the carbon price introduced by the Gillard government shows it had no detectable effect on kilometres flown and hence carbon emitted, despite being levied at A$23-$24 per tonne.

If Australia is to meet its Paris climate commitments, the National Energy Guarantee target will need to be raised or radical measures will be required, such as putting a hard cap on emissions in sectors such as aviation.

Our analysis of domestic aviation found no correlation between the Gillard government’s carbon price and domestic air travel, even when adjusting statistically for other factors that influence the amount Australians fly.

To reduce aviation emissions, a carbon price must either make flying less carbon intensive, or make people fly less.

In theory, a carbon tax should improve carbon efficiency by increasing the costs of polluting technologies and systems, relative to less polluting alternatives. If this is not possible, a carbon price might reduce emissions by making air travel more expensive, thereby encouraging people to either travel less or use alternative modes of transport.

Why the carbon price failed to reduce domestic aviation

The cost of air travel has fallen dramatically over the last 25 years. As the chart below shows, economy air fares in Australia in 2018 are just 55% of the average cost in 1992 (after adjusting for inflation).

A carbon price could incentivise airlines to reduce emissions by improving their management systems or changing plane technology. But such an incentive already existed in 2012-2014, in the form of high fuel prices.

A carbon price would only provide an additional incentive over and above high fuel prices if there is an alternative, non-taxed form of energy to switch to. This is the case for electricity generators, who can switch to solar or wind power.

What would meeting Australia’s Paris commitment require?

Given the failure of the carbon price to reduce domestic air travel, there are two possibilities to reduce aviation emissions by 26% on 2005 levels.

The first is to insist on reducing emissions across all industry sectors. In the case of aviation, the modest A$23-$24 per tonne carbon price did not work.

Hard caps on emissions will be needed. Given the difficulty of technological change, this will require that people fly less.

The second option is to put off reducing aviation emissions and take advantage of more viable sources of emissions reduction elsewhere.

By increasing the National Energy Guarantee target to well above 26%, the emission reductions in the energy sector could offset a lack of progress in aviation. This is the most economically efficient way to reduce economy-wide emissions, but does little to reduce carbon pollution from aviation specifically.

Airline emissions are likely to remain a difficult problem, but one that needs to be tackled if we’re to stay within habitable climate limits.

On May 10, the 43.5-metre schooner Avontuur arrived in the port of Hamburg. This traditional sailing vessel, built in 1920, transported some 70 tonnes of coffee, cacao and rum across the Atlantic. The shipping company Timbercoast, which owns and operates Avontuur, says it aims to prove that sailing ships can offer an environmentally sustainable alternative to the heavily polluting shipping industry, despite being widely seen as a technology of yesteryear.

Similar initiatives exist across the world. In the Netherlands, Fairtransport operates two vessels on European and transatlantic routes. In France, Transoceanic Wind Transport sails multiple vessels across the English Channel and Atlantic Ocean, and along European coasts. The US-based vessel Kwai serves islands in the Pacific. And Sail Cargo, based in Costa Rica, is building Ceiba, a zero-emission cargo sailing ship.

Transporting cargo by sail is both a practical response to climate change and a contribution to a larger debate.

These initiatives have an environmental objective: transporting cargo without generating greenhouse gas emissions. But are they really a viable alternative to today’s huge fossil-fuelled maritime cargo transport industry?

Shipping emission targets?

On April 13, 2018, the International Maritime Organization, the United Nations body that regulates shipping, agreed for the first time to limit the sector’s greenhouse emissions. It’s targeting a 50% reduction by 2050 (relative to 2008 levels), with the aim to phase out emissions entirely.

This was a breakthrough, given that both the 1997 Kyoto Protocol and the 2015 Paris Agreement exclude international shipping (and international aviation) from emissions targets, because these are so hard to attribute to individual countries.

Conventional seaborne cargo transport is relatively energy-efficient. It emits less greenhouse gas per tonne-kilometre (one tonne of goods transported over one kilometre) than transport by train, truck or plane. But because 80-90% of all goods we consume are transported by sea, the total emissions of the shipping industry are immense.

A recent report commissioned by the European Parliament raises further alarm bells, underscoring the fact that the sector’s huge growth is likely to swamp any carbon savings that come from improved operations. On top of this, the significant progress made in other industries means that the relative share of greenhouse gas emissions from cargo shipping is likely to increase from the current 2-3% to 17% by 2050.

Zero-emission vessels?

The OECD International Transport Forum is less pessimistic. It projects a 23% increase in the sector’s emissions between 2015 and 2035 on current trends, but also argues that it will be possible to decarbonise maritime transport altogether by 2035, through the “maximum deployment of currently known technologies”.

Meanwhile, the IMO faced a tricky balancing act in juggling the priorities of different countries. Climate-vulnerable nations such as the Marshall Islands want shipping emissions to be cut entirely by 2035. The European Union has proposed a reduction of 70-100% by 2050, while emerging economies such as Brazil, Saudi Arabia and India have argued against any emissions target at all. Despite these differences, the IMO did agree on a 50% reduction target by 2050 in April 2018.

Sail cargo

It took Avontuur 126 days to sail from France to Honduras, Mexico, Cuba and home to Germany. But conventional container ships can cross the Atlantic in about a week. Avontuur was carrying more than 70 tonnes of cargo on arrival in Germany. But many cargo vessels now carry more than 20,000 standard shipping containers (TEU), each weighing more than 2 tonnes and able to hold more than 20 tonnes of cargo.

Given the relatively small capacity of sailing ships, it is expensive and labour-intensive to ship cargo this way. But despite these limitations, support for sail cargo initiatives is growing. A consortium of small North Sea ports, for example, will “create sail cargo hubs in small ports and harbours, giving local businesses direct access to ethically transported goods”.

Ceiba, a new sailing vessel builds on traditional skills and incorporates new technologies to help attain global carbon emission targets.

These initiatives signal the revival of sail cargo with an explicit environmental agenda, although this effort is dwarfed by the scale of the global shipping industry. But while they don’t stack up in logistical terms, these voyages can help us see the possibilities for a world without fossil fuels. Sail cargo aims to rethink not only the means of propulsion for cargo vessels, but the entire scale, economy and ethics of cargo transport.

Traditional sailing vessels like Avontuur will not be able to compete with conventional cargo vessels on speed, scale or cost. But they help us focus on the underlying issue. We ship too much, too often and too far. The scale of shipping is unsustainable. That is why we need a change of mindset as much as a change of technology.

Sail cargo initiatives raise awareness about the devastating environmental effects of conventional cargo shipping. And they do so by showing that an alternative is possible. Indeed, it has been around for thousands of years.

What sorts of weather lead us to change our daily travel behaviour? How do we respond to scorching heatwaves, sapping humidity, snow and frost, strong winds, or torrential rain? International research shows weather is important in shaping our everyday movements.

Why do we care about the weather?

Firstly, how do we explain people’s common obsession with the weather? As Samuel Johnson put it:

It is commonly observed, that when two Englishmen meet, their first talk is of the weather; they are in haste to tell each other, what each must already know, that it is hot or cold, bright or cloudy, windy or calm.

Is this merely a keen (or indeed pathological) interest in the subject?

According to Kate Fox, these conversations are not really about the weather at all: weather-speak is a form of code, evolved to help Anglo-Australian people overcome their natural reserve and actually talk to one another. Weather-speak can be used as a greeting, as an ice-breaker, and/or as a “filler” subject.

But, beyond its use as a conversation prop and social bonding device, weather does play a major role in travel behaviour. And as the impacts of climate change unfold, the severity and frequency of extreme weather conditions are predicted to increase.

A better understanding of the dynamics of the relationship between weather and travel behaviour is thus essential in helping cities develop transport and planning responses appropriate to their conditions.

What do we know about the weather-travel relationship?

It’s complicated. Research on the weather-travel relationship has revealed that effects vary by mode of travel.

Active transport, such as walking and cycling, is the most vulnerable to variations in the weather. Arriving drenched is both uncomfortable and impractical, so we might drive rather than face this prospect. Wet weather forecasts are likely to trigger a travel mode shift as travellers opt for greater comfort and safety.

But the day of the week also affects these decisions. Inclement weather is more likely to reduce weekend and off-peak travel – the so-called discretionary trips – than standard weekday commute trips. Clearly, travel purpose plays a stronger role than weather.

Geographic variations across the transit network have been observed too. Bad weather has more serious effects in areas with less frequent services and without protected bus and rail stops. Travellers in areas with more frequent services and well-designed shelters appear to be less sensitive to bad weather.

High-density cities appear to reduce the impacts of weather on active transport, with this cyclist braving the rain in Osaka.Akuppa John Wigham/Flickr, CC BY

In areas with high population densities, the effect of weather also appears to weaken. This is particularly the case for active transportation such as cycling.

How we travel during inclement weather also involves more subtle changes. Trip chaining, or the process of stringing together multiple smaller journeys into a larger one, is reduced in complexity, particularly on rainy days.

In terms of “extreme” weather, not all types have the same effect. Heavy precipitation (snow or rain) and, to a lesser extent, extremely high or low temperatures appear to have a greater effect on travel behaviour than strong winds or high humidity.

Adapting to weather conditions

We cannot change the weather. But we can plan our transport systems to be more resilient and better shield us from the weather when we travel.

If we don’t do this, we will face the same crisis as Transport for London. Since its privatisation, its train services experience delays every autumn and winter due to “leaves on the line” and “the wrong type of snow”.

What kind of transport adaptations are available and work? The options range from offering passengers a more diverse choice of modes, to improving existing infrastructure. For example, making public transport stations more user-friendly could soften the impact of bad weather.

More seamless interchanges may have a strong effect, as commuters generally find modal transfers stressful. Temperature-controlled, covered or underground transfer stations would protect passengers while between modes of transport.

Active travel infrastructure is particularly important. Cities that are committed to supporting non-motorised transport have implemented or proposed bold policies.

Beyond these incremental interventions, a fundamental rethink of our urban design approach is necessary. The key to limiting and adapting to the effects of weather on travel may well be the “30-minute city”. But this can only be achieved through high densities and mixed land use – concepts that have so far generated fierce resistance and NIMBYism in Australia.

Another word of caution. What works in one climate zone might not work in another. This is because human bodies and minds adjust and develop different expectations and tolerance to weather and temperature patterns. For example, the optimal temperature range for cycling is as broad as 4-40°C in continental climates, but as narrow as 15-32°C in subtropical climates.